Solvent fractionation



NOV- 27, 1951 w. M. LEADERS ETAL SOLVENT FRACTIONATION Filed Jan. 17,1946 .Al jab NW. QW* F ...Y N IY mv 3 wv k |\|0h. m FZN JOW u ^w\\ M t vz mw ON a WM a u w LI k\ |.Y N 0 NM\ .N AI m..\. www v @N Q m a How NN NN d ...ru Al 9:5 dzb .AI 1 .5 Al um AI .5 QM! m @Y ww MN m\ e w s f M,\.Q\ WM.. {JNW IY l SW mm aw uw w) ww Patented Nov. 27, 1951 soLvENT'FRAoTI'oNATI/ William M. Leaders-and Felix E. Lacey, Chicago, Ill.,assignors to Swift & Company, Chicago, Ill.;- a `corporation of IllinoisApplication January 17, 1946, s'eriai No. 641312 This invention relatesto the treatment of fatty materials and has to do particularly with thetreatment of fatty materials with solvents to separate valuableconstituents therefrom.

The invention is applicable to the treatment of 3 Claims. (Cl. 2611-419)fats and fatty oils, either animal and vegetable,

such as greases and tallows, soybean oil, cotton- Vseed oil, linseedoil, fish oils, peanut oil, and sunflower seed'oil. FattyV acids derivedfrom the aforesaid oils may also be treated in accordance withthe`invention.

Commercial fats and fatty acids vare generally composed of components ofdifferent degrees vof saturation. The proportion of the saturated andunsaturated constituents varies with the different products, dependingon their origins. ample, fats and fatty/oils derived from animal sourcescontain from about'40% to 60% saturated compounds and the remainder ofunsaturated compounds of varying degrees of unsaturation.

For ex- Fatty oils of vegetable and marine origin usually posed ofcompounds having substantially the same degree of saturation. This isparticularly true in the manufacture `of paint oils and resins, in thecompounding of edibleproducts, and in the manufacture lof chemicalderivatives. For such specific purposes the fatty material becomes morevaluable as the degree of purity of the desired components is improvedin the product. As applied to commercial fats and fatty acids, theseparation is usually on the basis of the number of unsaturated bonds.Accordingly, it is possible to separate a fat and fatty acid intocomponents containing substantially saturated constituents, compoundshaving one double bond, compounds containing two double bonds andmaterials of even a higher degree of unsaturation.

An object of the present invention is to provide a more eiiicientprocess for the separation of fatty materials into components ofdifferent degrees of unsaturation.

Another object of the invention is to provide a process for thefractional separation of fatty materials to produce improved yields ofdesired products.

V.A further object of the invention is toprovide a process for thefractionation Vofv fatty-materials wherein a sharper separation betweenthe materials of different degreesfof unsaturation is obtained. v' "WAlso an object of the invention is to provide an improved processwhereby fatty materials may be separated intoproducts of improvedquality.

Heretofore attempts have been made to separate fatty materials into thevarious constituents by distillation, `and while some success lhas beenobtained inthe separationA of fatty acids into components of varyingdegrees of unsaturation by distillation, this method has not beenventirely satisfactory; The boiling points of certain saturated andunsaturatedrc'onstituents are so nearly alike, it is often difficult toobtain any substantial degree of separation by fractional distillation.

Attempts have also been made heretofore to separate the constituentsr offatty materials by seeding and crystallization of aportion of thematerial, particularly the more saturated components, and then theseparation ofthe crystals from the oily materials by pressing. Such aprocess is useful for the separation ofthe wholly saturated components,lbutr the method has not proved satisfactory for the fractionation of theunsaturated constituents.

It has also been proposediheretofore 'to fractionate fatty materials`with the aid of solvents. For exampla'fa'irly good success has beenobtained with the'separationof saturatedl compounds, such asstearine-from'animal :fats by the use of-a crystallization solvent. Somesuccess has also been obtained in the fractionation of unsaturatedcompoundsvby Vtheu'se of solvents both by crystallization yandliquid-liquid phase'fractionation.' However. infthe fractionationr offatty materials, on the basis of unsaturation with theuse of solvents,excessive amounts of solvents and `extreme temperatures are required,and even under 3 saturated components. We have found that liquid-liquidphase separation is more efficiently accomplished if the more saturatedconstituents are first removed, particularly such saturated constituentsas can be eciently separated by solvent crystallization.

It hasbeen proposed heretofore to separate a fatty material intosaturated/and unsaturated fractions and then fractionally distill thetwo fractions separately. Thus, the saturated constituents of a fattyacid mixture are separated from the unsaturated constituents by solventcrystallization. The two fractions are then subjectedl separately tofractional distillation. The process, however, is applicable only tofatty acids since glyceride oils cannot be separated by fractionaldistillation. Furthermore, high losses occur in the process on accountof the high temperatures required; for example, polymerization losses ashigh. as 15% are not uncommon.

The present invention contemplates a two-stage processjwherein the fattymaterial is rst subjected to solvent crystallization to separate themore saturated portion, .and then the lesser saturated portion issubjected to solvent fractionation yin a liquid-liquid phase `operationto separate the material into fractions of diiferent degrees ofunsaturation. The amount and type of materials separated in the rst stepof our process will depend on the nature of the materials treated. Ifthe material to be treated contains a substantial amount of saturatedconstitutents,

, the fraction separated in the first step will consist mainly ofsaturated materials. The latter .will usually be the case in treatingfatty acids derivedfrom tallow, greases, or mixtures of tallow andgrease of animal origin.

When treating glycerideoils, the fatty acids are often combined in aglyceride moleculeY in combination withV the.unsaturated fatty acidradicals present to give mixed triglycerides. Usually the materialseparated in the crystallization stage will be substantiallydi-saturated mono-unsaturated triglycerides, and will contain all of thetri-saturated fat present and a minor portion of di-unsaturated.mono-saturated material. In thisv way, substantially all the saturated:fattyacid groups present in the original -fatty material will beseparated as one or more of these triglycerides. Thek distribution ofthe Ifatty'acids in natural occurring fats is such as to practically`eliminate the presence of simple triglycerides. containing .threeradicals of the same fatty acids.. For. this reason, the degree ofseparation that is possible, even from a theoretical consideration, isless than when treating .fatty acids or mono-hydric esters of the fattyacids.

When treating materials containing very little or substantially novsaturated constituents in the first step of vour process, the fractionseparated in the first stage may not be a highly saturated Vmaterial butcontain substantial amounts of the less saturated materials. Forexample, in treating oils such as soybean oil, cottonseed oil, etc., thefraction initiallyseparated Will contain substantially all of thesaturated fatty acid groups present along with a considerable amount ofthe unsaturatedgroups of the lowest degree of unsaturation. With theoils just mentioned, the glycerides separated would be composedsubstantially of estersl of the fatty acids such as palmitic, oleic,andrlinoleic, with only minor amounts f .the estrsofmorehighly,unsaturated fatty acids..

In the second step of our process, We intend to fractionate materialsfrom the first stage of our process into two or more fractions ofvarying degrees of unsaturation. If the fatty materials treated arefatty acids, 'the fatty materials will be separated into fractionscontaining substantially one type of fatty acids. For example, onefraction will contain substantiallyvall of the oleic acid and the alliedfatty acids of one double bond. The next fraction will containsubstantially all of the linoleic acid and isomers containing two doublebonds. And the third fraction will contain linolenic acid and some lesshighly unsaturated fatty acids.

In treating fats and oils, a fractionation similar to that described inconnection with the fatty acids is desirable; However, the mixedcomposition of the triglycerides makes it impossible to obtain as high adegree of resolution when the individual fatty acids are combined asglycerides. The rst fraction will contain a substantial amount of estersof oleic acid with a minor portion of esters of linoleic acids andlinolenic acids combined as glycerides. The second fraction will containglycerides with substantial quantities of linolenic acids with minorquantities of oleic and linoleic. The third fractionY will containsubstantial quantities of linolenic acid and more highly unsaturatedfatty acids, with only minor quantities of oleic and linoleic acids.

The rst step of our process is essentially a crystallizing operationwherein the fatty material is mixed with the required amount of solventand the mixture chilled to cause crystallization of the more saturatedconstituents. The amount and type of material crystallized will dependupon the type and amount of solvent, the temperature and the nature ofthe fatty material treated. In carrying out this initial. step of theoperation one maybe lguided by the principles set forth above as .to thetype of materials to be crystallized, and this material may bepredetermined by iodine number, titer, melting point, thiocyanogenvalue, and, in the case of fatty acids, lead salt precipitation.

The amount of material crystallized in the rst step may vary from 10% to60%. For example, in the case of cottonseed oil, the amount will beapproximately 10% andin the case of tallow and fatty acids, as much as60%. Other materials may vary withinv the above range. The solutioncontaining vthe crystallized compounds is subjected to appropriateseparation operations, preferably filtration in. a continuous filter,wherein the crystallized portion is, `filtered from the solution. -A .e

We may use a number of solvents in the crystallization step includingboth polar and non-polar solvents, such as propane, butane, pentane,hexane and members of the alkane series up to decane; methyl and ethylalcohol; ethyl ether; carbon disulfide; B-Bl-dichlor ethyl ether; nitropropane; ,ethylene dichloride; acetone; methyl ethyl ketone; isopropylacetate; amylacetate; monomethyl ether of ethylene glycol; and monoethylether of ethylene glycol.

When using volatile solvents, for example, a normal gaseous solvent,such as propane or butane, we may obtain chilling of the solution byvaporization of a portion of the solvent. When using less volatilesolvents, chilling with an extraneous refrigerant is desirable.

In the second step of the process we prefer to further separate thefattymaterials treated in the first step into two or more fractions of gli??@84.1.

'varying degreeslof; unsaturation.; as. indicated by iodine value. Theproduct .,from., he .first stage may be chargedto. the second,` stagewith or without the addition of more of the same solvent or a differentsolvent. When using certain solvents, such as the ,normal gaseous hydro?carbons, for example, propaneor b utane, the solution from the rst stageAafter the separation ofthe crystallized fraction may bev chargeddirectly to the second stage. In case it is desired to use a dilerentsolventy in the second `stage than was used in the rst stage, then thesolvent employed in the initial stage maybe removed, all or in part,from the fatty material.

.In the case where two'solvents are to beused in the second stage, thesolvent used in the first stage may be retained ywith the fatty.material and charged directly to the sec-ond stagewherein asecondsolvent charge is introduced.'y For example, in the separation of `fattyacids using normally liquid hydrocarbonsr as a, crystallizing solvent, acombination of hydrocarbon-and furfural may be employed to accomplishthe separation in the second stage. l Y Suitable solvents that may beused alone in the second stage include furfural, sulfur dioxide,furfuryl alcohol, phenol, and nitro benzene.

When using such solvents, the solvent used in the first stage is usuallypartially or completely removed. Suitable 4solvents which may be used inboth stages of our process are butane, propane, acetone, hexane,beta-beta-dichlorethyl. ether, methyl Cellosolvefand ethyl Cellosolve.'When using the latter solvents all or a portion of. the solvent used inthe first stage may be used in the last stage.

' The operating conditions in the second step will vary depending on thetype and amounts of solvent and the nature of the oil treated. Theoperation is usually carried out .at above vroom temperatures and mayvary from slightly above room temperature, for example, 100 F. to 110 F.in the case of furfural, up to aroundv 200 F. in the case of propane.

When using a volatile solvent, such aspropane, sufcient pressure ismaintained to keep the solvent in the liquid phase. Such pressures maybe up to 650 pounds to '100l pounds per square inch. The s-olventtreatment may be conducted in' a batch, semi-batch, or continuoussystem. We prefer to use a continuous countercurrent tower wherein oneIfraction is drawn from the top of the tower and the :other fraction.from the bottom of the tower. In most cases the less unsaturatedfraction will be withdrawn from the top of the tower and the moreunsaturated fraction from the'bottom of the tower, but the relativepositions for drawing olf fractions of different degrees of unsaturationwill depend on the density of the solvent. For example, with a highdensity solvent the more Vsaturated fraction may be withdrawn from'thebottomof the tower and the more unsaturated fraction from the top of thetower.

The invention willV be more fully understood from the followingdescription read in connection with the accompanying drawing.y

Referring to the drawing, thev fatty material to be treated isintroduced through' the line i and forced by the pump 2 through theVmixer 3, wherein the oil is thoroughly mixed with the solvent which maybe introduced through the line 5 or the line 6. The mixerl may be any'suitable mechanism for vthoroughly mixing the solventl and oil,. suchasafspaddle typeA mixer,

2115x211u for. Creatiggftllrblilegtw 91 a passager provided Awith.orifices on b aiilesorl both', The pfoportionsof -theAsol'ynrent andthfoilwill usually bearoundfour to five parts of'solvent to one part ofoilby volume. Ihe solutionY of ouiland fatty'material is conductedthrough the line 8` to a chiller Y9. In the chiller the solution cooledtoal temperature sufficiently low to crystallize out the desired amountof more sat--V urated compounds.y The temperature in the chillervmayrange from` about +30 F. Vto as low as Yabout 70 F., depending onthe solvent and fatused. The chiller maybe a double pipe scraped walltype for the use of extraneous refrigerant or a simple enclosed tankfitted with a vapor escape lock for use with normally gaseoushydrocarbon or other low boiling, self-refrigerating solvent. If aself-refrigerating solventA used, the portion of the solvent vaporizedwill be removed through the pipe I0 and condensed and recycled to theysystem through the iine`6. The mixture of liquid and crystals from lthechiller 9 is conducted through line I2 to the filter I4. The lter ispreferably a rotary drum type filter and may be 'vapor tight for usewith volatile solvent and should be equipped t0r oper; ate ,under bothpositive pressure` and reduced pressures as low as 10mm. of mercuryabsolute. The crystallized portion of the fatty material along with somesolvent is discharged from the lter through the line I5 into`thestripper I6, wherein the solvent is stripped from the more saturatedfraction. The stripper may be operated under reduced pressure and withinjected steam, if necessary. The solvent is. removed from the upperportion of the stripper through the :line l1 and may be discharged fromthe system through the line I8 or recycled to the system through theline 20.v The more saturated fatty constituents are withdrawn from thelower portion of the stripper through the line 2|.

'Y VThe solution of fatty material and solvent separated as a filtratein the lter I4 is discharged through the line 23 and may be furthertreated in either of two ways. If it is desired to remove the solventfrom the fatty material at this stage, as may be the case when it ispreferred to use a different solvent in the second stage, the solutionis conducted through the line `24 to a still 25. In the still thesolvent may i;yejremoved all or in part as vapors. v'Ihe distilledsolvent may be removed from the system through the line 21 or recycledthrough the line 28. 'Y The bottoms vin the still containing the fattymaterial may be drawn off of the lower portion thereof through the line29 and conducted through the communicating line 30 to fractiona# tioncolumn 32. In some cases, as for instance When it is desired to use thesame solvent in the secondstage as was used in the first stage, thestill 25 may be by-passed and the solution in line 23 conducted throughthe line 3| and line 30 to the fractionation column 32.

While we have shown the charge line 30 as entering lthe fractionationtower in the upper section, the position for introduction of the fattymaterial into the fractionation tower will vary, vdepending on the typeof solvent used. In case v.the solvent density is greater than thedensity Vof the fatty material, as in the case of furfural, thefattymaterial will be introduced into the llower section of the tower andrise through the `falling tower of solvent. When the density of thesolvent is less than the fatty material, as

awash bons, such as propaneor buta-ne, the fattymaterial will `beintroduced into the upper portion of the tower and descend through arising column of solvent.- As an illustration, if the fatty materialcharged to the fractionation tower is the ltrate directly from thefilter l4--say, a solution of Vfatty material and propanethe solutionwould be chargedV into the upper portion of the tower. Additionalsolvent, which might be propane or butane, would be charged into thelower portion of the tower. the rst stage is removed in the still 'andthe straight fatty material is charged to the fractionation column, suchcharge may be introduced into the lower portion of the tower when it isintended to use a high-density solvent such as fu-rfural Vorbeta-beta-dichlorethylether, which solvent would be introduced into theupper portion of the tower. In the drawing we have shown the solventintroduced into the lower portion of the tower through the line 35. Suchposition of introducing the solvent is suitable when using a low-densitysolvent such as propane. When using a solvent which has a higher densitythan the fatty material, then the relative positions of introducing thesolvent and fatty material should be the reverse of those shown in thedrawing.

f The fractionation tower is operated under temperature and pressureconditions to maintain the solvent in the liquid phase and to cause aseparation of phases. The interface is ordinarily between the points ofintroduction of the solvent and of the fatty material. The materials aredrawn off from each phase from the top and bottom of the tower. Again,as shown in the drawing wherein a low density solvent is used, the upperlayer or phase containing the major portion of the solvent andrelatively rich in fatty material of lower degree of unsaturaton isdrawn oi from the top of the tower through the line 36 and dischargedinto the still 38. In the still the solvent is vaporized and removedthrough the line 39 or recycled to the system through the line 40. Line40 communicates with branch line 4|, whereby the solvent may be returnedto the first stage, and with the branch line 42, whereby the solvent maybe returned to the fractionation tower 32. The fatty material may bewithdrawn from the bottom of the still 38 through the line 45. The layercollected in the lower portion of fractionation tower 32 containing aminor proportion of the solvent and fatty `material relatively rich invmaterials of a higher degree of unsaturation is drawn from thebottom ofthe tower through the line 45 and discharged into the still 48. Solventremoved in still 48 may be returned through the line 49 and branch line50 to the fractionation tower 32 or through the line 49 and branch line5l to the first stage of -the system. Fatty material removed in thestill 48 may be withdrawn through the line 52.

For purposes of illustration, examples will now be given of theoperation of the invention. It is to' be understood, however, that theinvention is not limited to the specific examples.

'the solution of fatty acids, and this solution was ycharged to asolventl removal tower where apart If the solvent in- Cal f the solventwas removed from-the filtrate to give a Asolvent to fatty acid ratio ofapproximately ve to three by volume. This solution was charged directlyinto the lower section of a packed tower at two-thirds the rate ofcharge of furf-ural which was-utilized as a fractionating selectivesolvent and introduced into the upper portion of the tower. Thetemperature of the tower was about 89 F. in the upper portion and about88 F. in the lower portion. The interface was maintained approximatelyone-fourth the distance up from the foot of the column. A rainatefraction was withdrawn from the top of the tower and an extract waswithdrawn from the bottom of the column. The rafnate fraction contained50% petroleum ether, 13% furfural, and 37% fatty acids. The extractcontained 13% petroleum ether, 73% furfural, and 14% fatty acids. Theratio of rafiinate to extract was approximately one to three. Thisratiol of raffinate to extract, as well as the amount of solvents used,was determined experimentally so as to give approximately a 50-50distribution of the fatty acids in the raiiinate and extract. The iodinenumber of the fatty acids obtained in the raffinate was 82.5. The iodinenumber of the fatty acids in the extract layer had an iodine number of142.1. The crystallized fatty acids removed in the filtration stepamountedrto approximately 15% Vof the original charge and had an iodinenumber of 23.2 and a saponication number of 208.0. lThis fractionconsists mainly of palmitic acid in mixture with a small amount ofstearic acidand oleic acid.

Example 2 Soybean oil, having an iodine number of l37.6,

was dissolved in four volumes of propane at a temperature ofapproximately F. and 270 pounds pressure. The pressure was slowlyreduced to allow a small portion of the solvent to vaporize, therebycooling the solution. The rate of temperature drop was controlled atapproximately 1 F. per minute. The solution was cooled to 0 F. andfiltered. The solid fraction obtained in the lter amounted toapproximately 10% of the initial oil charged and had an iodine number of63.0. This fraction contained substantially all the combined saturatedVfatty acids present in the original soybean oil along with some oleicand a small amount of linoleic acids. The solution from the` ltrationoperation was passed throughv a heating zone and the temperature raised,to about 168 F. This warm solur tionwas introduced, under pressure,into a packed tower ooded with propane. The solution was introducedapproximately two-thirds of the way up from the bottom of the tower.Additional solvent,'amounting to fifteen volumes on the basis of the oilcharged, was introduced into the lower portion of the tower. Thefractionating tower was maintained at a temperavture of 178"v F. at ,thetop of the tower, dropping oif gradually to '170 l. at the lower portionor' the tower. The interface was maintained in K Suiiicient pressure wasmaintained in the tower to prevent vaporization of the solvent propane.The raffinate fraction, containing substantially all of the propane andthe more saturated oil, was removed from the upper portion of the tower.The extract fraction containing approximately 'one volume of solvent onthe basis of the oil, was

removed fromvthe bottom of the tower. These solutions of rainateandextract werev subjected -to a primary stripping operation to remove most`of the solvent and to a final step of steam stripping to remove thelast traces of the solvent. The rafnate fraction had an iodine number of91.5. The extract fraction had an iodine number of 165. Approximately64% of the higher iodine fraction kand about 36% ofthe lower iodinefraction calculated on the basis of the oil charged to the fractionatingcolumn were obtained.

Example "3 Cottonseed oil fatty acids,v having an iodine number of 114.2and a saponication value of 190.8, were` dissolved in four volumes ofpropane at 120 F. and 270 pounds pressure. The pressure was slowlyreduced and the solution chilled by the evaporation of a portion of thissolvent at arate of .1 F. per minute to a temperature vofl1" F.` Thesolution was filtered and the solid material washed with one-half avolume of cold solvent. The ltrate and the wash solution were .combinedand passed through a heating zone, where-.the temperature was raised to195 F.- This heated solution` was introduced into the middle section ofa packed fractionating tower into the lower portion of which was chargedan additional quantity of liquid propane, .amounting to forty-fivevvolumes on the basis of the fatty acidcharged'. Thek upper portion ofthe tower ywas maintained at 204- F. and the .lowerportion ofthe columnat 197 F. Necessary heat to maintain this temperature and thetemperature gradient was supplied by a series of electrical heatingcoils spaced throughout the length of the tower. The overhead fraction,containing substantially all 'of the propane and the more saturatedfatty acids, gave a fatty acid with an iodine number of 87.5 and asaponification value of 188.0. The bottom fraction, containingapproximately one volume of solvent to fatty acids, had an iodine numberof 134.2 and a saponii'lcation value of 196.5. The iodine number of thesolid fraction separated in the filter vwas 11.0. ,A

Example! j Cottonseed oil`Y was -degummed-by treating the oil with 2%lwater at 160 F. and settling the gums.' volumes of acetone at atemperature of about 1'l0 F. to insure complete solution. The Y resultingsolution was slowly agitated and passed through a chiller wherein thetemperature was gradually decreased by the use of cold brine solutioncirculating in a coil. The temperature of the solution was lowered atthe rate of approximately 1 F. per minute to a temperature of about 30F. A precipitate began to appear as the temperature reached 40 F. and aslurry developed slowly as the temperature ,was further reduced. Thechilled slurry was passed through a filter operating under reducedpressure to remove the solid portion from the filtrate. The filter cakewas washed with one-half volume of cold acetone and the wash solutioncombined with the filtrate. The filter cake, which amounted to about ofthe original oil charged, was melted and the solvent removed. The solidproduct had a free fatty acid content of 1.8% and an iodine number of63. The combined filtrate and wash was introduced into a still whereinthe solvent was removed under vacuum. The last traces of solvent wereremoved Thedegummed oil was mixed with four y Lil) by a five-minutesteam stripping operation at a temperature of about F. under reducedpressure. The oil fromzthesolventV removal process was introduced intothe upperfportion ofr a continuous countercurrent fractionating tower.Into the lower portionof the tower forty volumes of liquid propane'wereintroduced for every volume of the oil. The tower temperature wasmaintained at around F. A 5 .temperature gradient was maintainedthroughout the length of the fractionating tower, the higher temperaturebeing maintained at the top of the tower. Two fractionswere'continuously removed from the tower; one from the top and one fromthe bottom. The bottom fraction, consisting'of approximately50% voftheoil charge and containing a small percentage ofY solvent,`was passeddirectly to a solvent Arecovery unit wherein the propane Wasremovedunder atmospheric pressure.A Finalremovaln of= Vpropane was'accomplished by steam stripping 'at approximately 225 F. andatmospheric. pressure. -The bottom fraction vhad an' iodine lnumber of131.0. The fraction removed from: the top of the tower contained a largeproportion of the "solvent and the other 50% of the'oil.' The productwas preheated to 200 F. and introduced into a solvent recovery tower,wherein the propane was removed under atmospheric pressure.' A steamstripping operation at'atmospheric pressureA of 225 F. was used as thenal step in the solvent removal. '.The top -fraction had an iodinenumber of 86.5 and a free fatty` acid content of approximately 1%.

y Example 5 Afsample ofncottonseed' oil' was subjected to acrystallization operation similarfto' that described in Example4,"aboveif The filtrate from the filter was denuded of solvent'iirastill. The oil vwas then introduced into the lower section of. aycountercurrent fractionatingA tower. Into the upper portion `of thetower two volumes of furfural .to one of oil were introduced. Theinterface between the two liquid phases was maintained at approximatelyone-third" of the Ldistance up from the bottom-of the tower. An averagetemperaturev of about 100 F. was kmaintained in 'the tower;Ithe'temperature gradient from the" bottom to the'- top of the' towerAbeing about 3 F.V An extract fraction containing'the majority of thesolvent and approximately 50% of the oil was removedy from lthe bottomof the tower. A raffinate,` containing approximately 20% solvent and theother..50% of the charged oil was drawn fromthe top of thetower. Thesesolutions were-introduced into separate lsolvent recovery'units afterpre-heating to a temperature of 250 C. The solvent recovery units weretwo-stage processes operated under high vacuum, the first stage being asimple fractional distillation, and the second a steam strippingoperation at about 200 C. and around ten millimeters absolute pressure.The solvent furfural remaining in the oil was reduced to less than onepart in ten million and showed only a faint test by the analine-aceticacid testing procedure, which is the common method of detecting tracesof furfural. The overhead raffinate fraction had an iodine number of91.5 and the extract fraction had an iodine number of 130.2. The extracthad a free fatty acid content of approximately 1.3%. It will be notedthat in this example the fatty acids are selectively withdrawn with thehigher iodine fraction, whereas by the use of propane, as in Example 4,the fatty acids were selectively withdrawn with the lower iodinefraction.

The presentinventionhas the 'advantage of Vproviding a process wherein asingle solvent may 'be used forrseparating a saturated portion of afatty material and' then the same'solvent used for fractionating -theremainder of the fatty Vmaterial into fractions of different degrees ofVespecially in the more unsaturated fractions where excessivetemperatures cause polymerization and heat bodying.

A further advantage of the invention is that the saturated materialpresent in the charged stock is removed by a simple method whicheliminates one of the interfering elements normally encountered in aliquid-liquid phase extraction. By separating the saturated materialfirst we are not troubled by the common phenomenon of the saturation ofour selective solvent with this-saturated phase and we are able toobtain in a single countercurrent operation a much greater degree ofresolution between the various unsaturated constituents present.

Obviously, manyV modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spiritand scope thereof, and therefore. only such limitations should beimposed as are indicated in the appended claims.

We claim:

1; A process for the treatment of fatty materials containing relativelysaturated and unsaturated constituents to obtain an improved separationof the highly unsaturated constituents, which comprises: rst cooling asolution of the fatty material in a liquefied normally gaseoushydrocarbon as a solvent to a temperature of between +30 and .-.70' F.by evaporation of a portion of the solventV to crystallize between and60 percent ofthe more saturated constituents from the solution, andfiltering the crys- -tals from the solution; then warming the solutionfree of the more saturated constituents in the presence of additionalnormally gaseous hydrocarbon as solvent to an elevated temperature andpressure to form two liquid phases. separatring thev phases andlrecovering from the separated phases constituents of the fattymaterlalhaving a higher andlower iodine value respectively. Y

2.*A process for the treatment of fatty materials containingv relativelysaturated and unsaturated constituents to obtain an improved separationof theV highly unsaturated constituents, which comprises: first coolinga solution of the fatty material in a liquefied normally gaseoushydrocarbon acting as a solvent to a temperature between ,-i-SO" and F.whereby between l0 and 60 percent of the more saturated constituentscrystallize from the solution, and separating the crystals byfiltration;V then subjecting the resulting solution containing the moreunsaturated constituents free of the more saturatedV constituents tocountercurrent extraction in the presence of additional normally gaseoushydrocarbon as solvent at an elevated temperature and pressure wherebythe solution separates into two liquid'p'hases, one of said phasescomprised substantially of constituents having an iodine value of atleast 40 points higher than that of the other phase, and separating saidphases.

3. A process substantially as described in claim 2 wherein the step ofcrystallization is carried out in propane as the solvent and thecountercurrent extraction step is carried out at a temperature betweenabout and 200 F. and at an elevated pressure between about 650 and 700p. s, i.

WILLIAM M. LEADERS.

FELIX E. ,LACEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Great Britain Dec. 7, 1933

1. A PROCESS FOR THE TREATMENT OF FATTY MATERIALS CONTAINING RELATIVELYSATURATED AND UNSATURATED CONSTITUENTS TO OBTAIN AN IMPROVED SEPARATIONOF THE HIGHLY UNSATURATED CONSTITUENTS,, WHICH COMPRISES: FIRST COOLINGA SOLUTION OF THE FATTY MATERIAL IN A LIQUEFIED NORMALLY GASEOUSHYDROCARBON AS A SOLVENT TO A TEMPERATURE OF BETWEEN +30* AND -70* F. BYEVAPORATION OF A PORTION OF THE SOLVENT TO CRYSTALLIZE BETWEEN 10 AND 60PERCENT OF THE MORE SATURATED CONSTITUENTS FROM THE SOLUTION; THENFILTERING THE CRYSTALS FROM THE SOLUTION; THEN WARMING THE SOLUTION FREEOF THE MORE SATURATED CONSTITUENTS IN THE PRESENCE OF ADDITIONALNORMALLY GASEOUS HYDROCARBON AS SOLVENT TO AN ELEVATED TEMPERATURE ANDPRESSURE TO FORM TWO LIQUID PHASES, SEPARATING THE PHASES AND RECOVERINGFROM THE SEPARATED PHASES CONSTITUENTS OF THE FATTY MATERIAL HAVING AHIGHER AND LOWER IODINE VALUE RESPECTIVELY.